In the past, facial makeup compositions have taken the form of grease sticks, creams, or pressed powder cakes. More recently dry, pressed powder makeup sticks have been developed. The pressed powder sticks provide a matte, non-greasy finish on the skin which will not smear as do grease sticks or creams. As a further advantage, the pressed powder stick can be applied directly to the skin without the use of brushes, puffs, or the like.
A pressed powder stick cannot be satisfactorily prepared by conventional molding techniques due to the fact that the powder composition is relatively dry and contains generally less than 35% by weight of water. This dry powdered mixture lacks sufficient fluidity to enable the powder to be molded by standard processes. Incorporating additional water with the powdered mixture to improve the fluidity is not feasible, as the evaporation of the water, after molding of the sticks, leaves voids in the structure.
Pressed powder sticks have been prepared in the past by extrusion methods. However, the use of standard extrusion apparatus has not proven entirely successful, because of the relatively dry and abrasive nature of the powder composition. It has been found that employing a hydraulic extrusion apparatus, in which a hydraulic ram is used to extrude the powder mixture through an axial orifice, will result in the water being squeezed from the powder mixture. Squeezing the water from the powder mixture further reduces the fluidity of the powder and increases the frictional resistance of the mass, thereby generating heat and evaporating additional water from the powder mixture to compound the problem. Thus, in the past, pressed powder sticks have not been successfully extruded on a commercial scale due to the dry and abrasive nature of the powder mixture.